The present invention relates in general to apparatus for wrapping groups of products and, in particular, to a semiautomatic apparatus for wrapping groups of products arranged on pallets suitable for transporting the products.
In the field of designing and constructing machines for wrapping palletised products, manufacturers have, over time, adopted two different constructional philosophies which have led to the definition of two different categories of machines, namely, fully automatic machines and semiautomatic machines.
Both these categories of machines have a similar basic structure comprising a platform for the pallet that supports the groups of products to be wrapped and a frame which is positioned at the side of the platform and on which a reel of wrapping film is mounted.
In the case of automatic machines, there are solutions where the platform rotates and the reel moves only vertically up and down in order to unwind the film so that it covers the entire group of products, or solutions where the platform is fixed and the reel moves up and down mounted on an arm that rotates around the group of products.
For semiautomatic machines, the first of the above solutions adopted for automatic machines is usually used, that is to say, the rotating platform and the film reel moving only vertically in both directions. The essential difference between the two categories of machines is that, in automatic machines, a number of operations required to start and end the wrapping cycle (for example, positioning the free end of the film close to the group of products, cutting the film after it has been unwound around the products, sealing the end of the film on the group of wrapped products, etc.) are performed by automatic devices without the direct action of an operator, whereas semiautomatic machines require an operator to enable these operations to be performed.
Obviously, this basic difference means that automatic machines are very expensive, used only for high productivity and at the top end of the market, while semiautomatic machines are economically better suited to companies with small to medium production levels.
In order to reduce the gap between these two categories of machines, the Applicant designed and constructed a semiautomatic machine where the film cutting operation is automated (see patent application WO 01/05661). In this solution, the machine comprises a film gripping and tearing unit mounted outside the profile of a platform. The gripping and tearing unit intercepts at least one portion of film of a certain width, located between the product group and the reel after the product group has been wrapped on the platform. Then, acting in conjunction with a partial rotation of the platform, the unit tears the film off the reel at the intercepted portion.
This unit, while it does not significantly affect the cost of the machine and leaves the structure and functions of current semiautomatic machines unchanged, constitutes a notable improvement in that it automatically performs two important operations, namely, cutting the filmxe2x80x94this being accomplished by tearing the film as the platform rotates, while withholding the end of the film still attached to the reelxe2x80x94and then transferring the end of the film to a gripper mounted on the platform, thus preparing the machine for the next wrapping cycle.
Tests have shown, however, that the trailing end of the film, which is gathered up and narrowed as a result of the tearing operation and which, after being torn, forms part of the wrapping on the group of products, may remain loose and does not always adhere perfectly to the surface of the wrapping. This is due to the fact that the adhesive properties of the film are not by themselves always sufficient to hold the end of the film down against the rest of the wrapping wound around the products. As a result, subsequent handling of the pallet may cause the wrapping to slacken and come away from the products.
The present invention therefore has for an object to overcome the above mentioned disadvantage by providing a semiautomatic apparatus capable of completely and efficiently wrapping the group of products without changing basic machine structure.